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SN65HVD1781: Termination Resistor on Both Side

Kunal barot
Intellectual 605 points
Part Number: SN65HVD1781

Hi Support Team

WE have used SN65HVD1781QDRQ1 in my Product (RS 485 Master) , we route the D+ and D- signal external , where user can connect other RS 485 Device. My Deice has termination resistor of 120 ohm. Does customer device (external device) also need termination resistor at their end too.

what if only 1 master (my device) and only 1 salve is connected on line, do we need termination resistor on both end. 

  • 0
    TI__Guru 62910 points
    Hi Kunal,

    In general, terminating the link at both ends will provide the best signal integrity by minimizing reflections occurring both in the master-to-slave direction as well as the slave-to-master direction (assuming a bidirectional communication link). Many applications can tolerate some reflections, though, especially if the data rates used are not very high, and termination is not required for an RS-485 transceiver to function. So, the answer to this ends up being a bit system-dependent. If you are able to measure the A and B signals on an oscilloscope at each end of the link, it will give you a better idea of the quality of the signals being received.

    Max